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cranelift: Add a conditional branch instruction with two targets (#5446)

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Add a conditional branch instruction with two targets: brif. This instruction will eventually replace brz and brnz, as it encompasses the behavior of both.

This PR also changes the InstructionData layout for instruction formats that hold BlockCall values, taking the same approach we use for Value arguments. This allows branch_destination to return a slice to the BlockCall values held in the instruction, rather than requiring that we pattern match on InstructionData to fetch the then/else blocks.

Function generation for fuzzing has been updated to generate uses of brif, and I've run the cranelift-fuzzgen target locally for hours without triggering any new failures.
This commit is contained in:
Trevor Elliott
2023-01-24 14:37:16 -08:00
committed by GitHub
parent ec6922ff24
commit b58a197d33
35 changed files with 943 additions and 159 deletions
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64
cranelift/interpreter/src/step.rs
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@@ -7,8 +7,8 @@ use crate::value::{Value, ValueConversionKind, ValueError, ValueResult};
use cranelift_codegen::data_value::DataValue;
use cranelift_codegen::ir::condcodes::{FloatCC, IntCC};
use cranelift_codegen::ir::{
types, AbiParam, Block, ExternalName, FuncRef, Function, InstructionData, Opcode, TrapCode,
Type, Value as ValueRef,
types, AbiParam, Block, BlockCall, ExternalName, FuncRef, Function, InstructionData, Opcode,
TrapCode, Type, Value as ValueRef,
};
use log::trace;
use smallvec::{smallvec, SmallVec};
@@ -236,8 +236,7 @@ where
// Retrieve an instruction's branch destination; expects the instruction to be a branch.
let continue_at = || {
let block = inst.branch_destination().unwrap();
let continue_at = |block: BlockCall| {
let branch_args = state
.collect_values(block.args_slice(&state.get_current_function().dfg.value_lists))
.map_err(|v| StepError::UnknownValue(v))?;
@@ -248,9 +247,9 @@ where
};
// Based on `condition`, indicate where to continue the control flow.
let branch_when = |condition: bool| -> Result<ControlFlow<V>, StepError> {
let branch_when = |condition: bool, block| -> Result<ControlFlow<V>, StepError> {
if condition {
continue_at()
continue_at(block)
} else {
Ok(ControlFlow::Continue)
}
@@ -279,17 +278,48 @@ where
// Interpret a Cranelift instruction.
Ok(match inst.opcode() {
Opcode::Jump => continue_at()?,
Opcode::Brz => branch_when(
!arg(0)?
.convert(ValueConversionKind::ToBoolean)?
.into_bool()?,
)?,
Opcode::Brnz => branch_when(
arg(0)?
.convert(ValueConversionKind::ToBoolean)?
.into_bool()?,
)?,
Opcode::Jump => {
let block = inst.branch_destination()[0];
continue_at(block)?
}
Opcode::Brif => {
if let InstructionData::Brif {
arg,
blocks: [block_then, block_else],
..
} = inst
{
let arg = state.get_value(arg).ok_or(StepError::UnknownValue(arg))?;
let condition = arg.convert(ValueConversionKind::ToBoolean)?.into_bool()?;
if condition {
continue_at(block_then)?
} else {
continue_at(block_else)?
}
} else {
unreachable!()
}
}
Opcode::Brz => {
let block = inst.branch_destination()[0];
branch_when(
!arg(0)?
.convert(ValueConversionKind::ToBoolean)?
.into_bool()?,
block,
)?
}
Opcode::Brnz => {
let block = inst.branch_destination()[0];
branch_when(
arg(0)?
.convert(ValueConversionKind::ToBoolean)?
.into_bool()?,
block,
)?
}
Opcode::BrTable => {
if let InstructionData::BranchTable {
table, destination, ..